# Copyright 2024 Databricks
# SPDX-License-Identifier: Apache-2.0

import torch
import torch.nn.functional as F

from megablocks.layers.arguments import Arguments


class FFN(torch.nn.Module):

    def __init__(self, args: Arguments):
        super().__init__()
        self.w1 = torch.nn.Parameter(
            torch.empty(
                args.hidden_size,
                args.ffn_hidden_size,
                device=args.device,
                dtype=torch.float16 if args.fp16 else torch.float32,
            ),
        )
        self.w2 = torch.nn.Parameter(
            torch.empty(
                args.ffn_hidden_size,
                args.hidden_size,
                device=args.device,
                dtype=torch.float16 if args.fp16 else torch.float32,
            ),
        )

    def forward(self, x):
        return torch.matmul(
            F.gelu(torch.matmul(x, self.w1), approximate='tanh'),
            self.w2,
        )


class GLU(FFN):

    def __init__(self, args: Arguments):
        super().__init__(args)
        self.v1 = torch.nn.Parameter(
            torch.empty(
                args.hidden_size,
                args.ffn_hidden_size,
                device=args.device,
                dtype=torch.float16 if args.fp16 else torch.float32,
            ),
        )

    def forward(self, x):
        x1 = F.gelu(torch.matmul(x, self.w1), approximate='tanh') * torch.matmul(x, self.v1)
        return torch.matmul(x1, self.w2)
